Flickr have added an interesting new feature to their query API, Machine Tags. In one way, this is really a formalisation of what people were already doing to a certain extent informally. What is seems like to me is a step toward RDF (at the moment there’s only support for literal values as objects)
# Can I define another machine tag as the value of a machine tag?
Sure, but it will not be processed as a machine tag itself.
and Dan Catt of Flickr says
It’s sort of, but Not Quite RDF forced into tags. (NQRDF)
via Danny
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